Among men, prostate cancer is the most common non-skin cancer. Although the majority of prostate cancer patients are over 65 years of age, outcomes data specific to elderly patients are sparse. This proposal addresses a pressing public health issue: What are the long-term clinical outcomes of the ever-increasing number of elderly patients with localized prostate cancer? This study will focus on outcomes following conservative management and primary androgen deprivation therapy (PADT), the second most common treatment among elderly men despite the absence of data supporting its application. The importance of determining the appropriate use of PADT has increased in urgency because a growing body of literature now demonstrates that ADT use is associated with substantial side effects and healthcare costs. The Institute of Medicine has identified assessment of treatment for localized prostate cancer as a top research priority in its recent comparative effectiveness research priorities report. During the initial funding period we found that survival outcomes have improved substantially over time and early use of PADT was not associated with improve cancer-specific or overall survival for the majority of elderly men with localized prostate cancer. These findings have been cited in numerous treatment guidelines. The major limitations of our initial investigation were limited follow-up and unavailability of key prognostics factors such as detailed Gleason scores and baseline prostate specific antigen (PSA) data. To address these limitations we are proposing a continuation study to provide longer follow-up data and refined outcome estimates incorporating newly available PSA and detailed Gleason scores. This population-based study will use SEER-Medicare linked data (1992 - 2011) to identify study subjects and cancer treatment history. The large sample size (N ~ 66,000) will provide ample statistical power. We will utilize modern methods designed to minimize biases. When complete, this proposed study will provide the largest and longest follow-up data (up to 19 years) on survival and on use of major interventions for cancer complications among elderly men with localized prostate cancer. Our updated data will help clarity any misconception about the potential benefit of PADT, thereby facilitating informed decision-making, decreasing inappropriate treatment, and thus reducing healthcare expenditures while improving quality of life for millions of men.